Arsene Wenger's side did lose some rhythm in the first part of the second half as Hull pressed their opponents higher up the pitch. But they failed to seriously stretch Gunners keeper David Ospina.

England forward Theo Walcott, 24, played 75 minutes on his first Gunners start for exactly a year as he continues to make his comeback from a serious knee injury and showed brief flashes of his pacy threat.

A Santi Cazorla pass allowed Sanchez to clinically fire in as Arsenal continue their bid to become only the eighth club to retain the FA Cup.

Hull City manager Steve Bruce:

"If we're going to be honest Arsenal deserved to win. We just needed to stay in there but unfortunately, at the top end of the pitch, we were unable to create anything.

"The disappointing thing for me is that the first goal is the first we've conceded from a corner this season. Mertesacker is huge - we should be doing better than that. We battled on valiantly but we weren't quite good enough.

"I know most teams get injuries but we can't carry six or seven missing - that's what we were doing today. We were down to the bare bones but there are no excuses, the better team won."

Per Mertesacker scored his first Arsenal goal since last season's FA Cup semi-final against Wigan

Arsenal sealed their passage into the fourth round through Alexis Sanchez's 16th goal of the campaign

Theo Walcott made his first Arsenal start since their FA Cup win against Spurs on 4 January last year

Arsenal came back from a 2-0 deficit to beat Hull in last year's final - their first silverware in nine seasons